We plan to continue our studies on the pathophysiology of diarrhea with emphasis on carbohydrate-induced diarrhea and on the correlation between the migrating inter-digestive motor complex (MIC) and bolus propulsion in the small intestine. Short-chain fatty acid (SCFA) absorption will be further investigated during colon perfusions in man. In these and similar studies of the human ileum particular attention will be paid to alterations in luminal HCO2 and pCO2; evidence for mutual inhibition (acetate-propionate-butyrate) will be sought. In everted sacs of rat colon mucosa we will study SCFA metabolism, absorption kinetics; effects of metabolic inhibitors and acetazolamide, as well as SCFA effects on Isc. Cecum stool balance studies of cecally instilled glucose will be performed in man at doses which serve as models for CHO-induced diarrhea. Small intestinal function and contents in lactose-induced diarrhea will be assessed. Separate studies will explore the effects of the MIC and of elevated circulating motilin on small investinal bolus propulsion and flow rate. We will continue our attempts at correlating elevated eneteric hormone levels with small intestinal dysfunction in patients with the WDHA syndrome.